1. Field of the Invention
The present invention relates to a fuel spraying apparatus of a gas turbine engine and more particularly to a fuel spraying apparatus of a gas turbine engine for realizing stabler combustion in composite combustion combining two kinds of combustion systems of a diffusion combustion system and a lean combustion system.
2. Description of the Related Art
It is an urgent necessity for environmental conservation to reduce harmful material ejected by combustion of an internal combustion engine. However, in a gas turbine engine, particularly in a large engine or an airplane engine, the pressure ratio is apt to increase on demand of realization of high output, and in correspondence to it, realization of high temperature and high pressure at the entrance of a combustor is promoted. As a result, an increase in the generation amount of NOx (nitrogen oxide), which is one of the harmful material aforementioned, is caused.
Therefore, in order to reduce the generation amount of NOx in the gas turbine engine, combustion systems such as the lean combustion system and rich burn quick quench lean burn (RQL) system are proposed and gas turbine engines using these combustion systems are partially put into practical use.
However, the aforementioned lean combustion system to realize low NOx is deficient in combustion stability at a low load. In order to overcome this problem, a composite combustion system combining two kinds of combustion systems of the diffusion combustion system and lean combustion system is proposed (refer to Patent Documents 1, 2, 3, 4, and 5 listed below).
Namely, the lean combustion system is required to introduce a large amount of air from the fuel spraying apparatus, so that the local fuel density in the combustion area is greatly lowered than the fuel density at the diffusion combustion system, and a problem arises that the ignitableness and combustibleness at a low load are degraded. Therefore, the composite combustion system intended to overcome the aforementioned problem by combination of the diffusion combustion system and lean combustion system, which is excellent in combustion stability, attracts a great deal of attention.
However, in the composite combustion system, a large amount of air introduced for lean combustion adversely affects combustion by the diffusion combustion system. Due to this adverse effect, a problem arises in combustion by the diffusion combustion system that sufficient ignitableness and flamableness and the combustion stability at a low load may not be obtained.
Particularly, for an airplane gas turbine, sure ignition is required under the condition of low temperature and low pressure at a high altitude, and emission at a low load at time of idling is regulated in various aspects, so that the degradation in the ignitableness and combustion stability due to air introduced for lean combustion may come into a greater problem.
Patent Document 1: Japanese Patent Laid-Open Publication No. 5-87340
Patent Document 2: Japanese Patent Laid-Open Publication No. 2002-115847
Patent Document 3: Japanese Patent Laid-Open Publication No. 2002-139221
Patent Document 4: Japanese Patent Laid-Open Publication No. 2002-168449
Patent Document 5: Japanese Patent Laid-Open Publication No. 2003-4232